<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .ang {
            display: block;
        }
        
        .change {
            display: none;
        }
    </style>
</head>

<body>
    <div class="he">
        欢迎页面
        <ul class="change">
            <li>hello</li>
            <li>world</li>
        </ul>
    </div>
    <script>
        var change = document.querySelector('.change');
        var he = document.querySelector('.he');
        var count = 0;
        he.onclick = function() {
            if (count % 2 == 1) {
                change.className = 'change';
            } else {
                change.className = 'ang';
            }
            count++;
            console.log(count);
        }
    </script>
</body>

</html>